Catalyst compositions similar to those of the present invention are known for the oxidation of acrolein to acrylic acid. For example, the disclosure in U.S. Pat. No. 3,567,773 shows catalyst compositions containing the elements of molybdenum, vanadium and tungsten; German Pat. No. 2,456,100 discloses catalysts having the composition of molybdenum, vanadium and tungsten in combination with such elements as copper, cobalt and iron; and Belgian Pat. No. 773,851 discloses the catalyst composition antimony, molybdenum, vanadium and tungsten and which may also contain titanium among other elements.